Emphasising the professional development of early career teachers, with an emphasis on pedagogy, is an obvious priority in improving student outcomes. Surprisingly then, in all the rhetoric around mentoring early career teachers (ECTs) this emphasis appears to be missing. This study explores the implications of professional development for ECTs in a particular pedagogical skill, in this case cooperative learning (CL), and the impact of this on the quality of teaching of two early career teachers. An abundance of research literature, over a significant number of years, argues that by focussing on cooperative learning as a pedagogical strategy, students’ social and academic outcomes will improve. This paper advocates ECTs expert use of CL to ensure this increase in both social and academic outcomes. The importance of this focus on pedagogy for ECTs as they use CL more in their classrooms is explored by analysing pre and post classroom observations, both in CL and in Quality teaching, as well as semi-structured teacher interviews. These are analysed to investigate teachers’ implementation of the cooperative learning strategy, to evaluate their understanding of classroom practice in CL and its impact on the quality of their teaching. The teacher with more years of experience made gains in both cooperative learning and quality teaching demonstrating an emphasis on pedagogy was significant in enhancing her professional accomplishment. The teacher with less experience struggled with other aspects of beginning teaching, such as school context and burnout, which had an effect on the overall quality of her teaching.